2014 YAMAHA YZ250F Owners Manual

REAR BRAKE
4-21
EAS1SM1148
REAR BRAKE
Removing the rear brake caliper
Order Part name Q’ty Remarks
Brake fluidDrain.
Refer to “BLEEDING THE BRAKE SYSTEM”
on page 3-21.
1 Protector 1
2 Union bolt 1
3 Copper washers 2
4 Rear brake hose 1
5 Brake pad pin plug 1
6 Brake pad pin 1
7 Rear brake pad assembly 2
8 Rear brake caliper bracket 1
9 Brake pad springs 2
10 Rear brake disc cover 1
11 Rear brake caliper assembly 1
For installation, reverse the removal proce-
dure.
2
3
4 11
56
79
1
8
9 10
2.5 Nm (0.25 m•kgf, 1.8 ft•Ibf)T.R.
10 Nm (1.0 m•kgf, 7.2 ft•Ibf)T.R.
10 Nm (1.0 m•kgf, 7.2 ft•Ibf)T.R.
17 Nm (1.7 m•kgf, 12 ft•Ibf)T.R.
30 Nm (3.0 m•kgf, 22 ft•Ibf)T.R.
New
S
7 Nm (0.7 m•kgf, 5.1 ft•Ibf)T.R.

REAR BRAKE
4-22
Disassembling the rear brake caliper
Order Part name Q’ty Remarks
1 Brake caliper piston 1
2 Brake caliper piston dust seal 1
3 Brake caliper piston seal 1
4 Bleed screw 1
For assembly, reverse the disassemble pro-
cedure.
1
2
3
4
S
BF
T R..6 Nm (0.6 m kgf, 4.3 ft Ibf)

REAR BRAKE
4-23
Removing the rear brake master cylinder
Order Part name Q’ty Remarks
Brake fluidDrain.
Refer to “BLEEDING THE BRAKE SYSTEM”
on page 3-21.
1 Union bolt 1
2 Copper washers 2
3 Brake hose 1
4 Split pin 1
5 Plain washer 1
6Pin 1
7 Brake master cylinder reservoir cap 1
8 Brake master cylinder reservoir diaphragm plate 1
9 Brake master cylinder reservoir diaphragm 1
10 Rear brake master cylinder 1
For installation, reverse the removal proce-
dure.
1
2
3
4 7
5 8
6 9
T R..
T R..
10
T R..

REAR BRAKE
4-24
Disassembling the rear brake master cylinder
Order Part name Q’ty Remarks
1 Dust boot 1
2 Circlip 1
3 Push rod 1
4 Brake master cylinder kit 1
For assembly, reverse the disassemble pro-
cedure.
4
3
2
1
BF
S
New
New

REAR BRAKE
4-25
EAS1SM1149INTRODUCTIONEWA14300
WARNING
If you need to disassemble the disc brake
components, observe the following precau-
tions.
• Never disassemble the brake components
unless absolutely necessary.
• If there is any problem with connections
on the hydraulic brake system, perform
the following jobs.
Disassemble the brake system, drain the
brake fluid, and clean it. After that, add a
suitable amount of brake fluid. Then, bleed
it after reassembly.
• Use only brake fluid for washing internal
brake components.
• Use new brake fluid for cleaning the brake
components.
• Immediately wipe off the spilled brake fluid
to avoid damage to painted surfaces or
plastic parts.
• Handle brake fluid with special care not to
let it enter your eyes so that you may not
lost your eyesight.
• FIRST AID FOR BRAKE FLUID ENTERING
THE EYES:
• Flush with water for 15 minutes and get
immediate medical attention.
EAS1SM1150CHECKING THE REAR BRAKE DISC
1. Remove:
• Rear wheel
Refer to “REAR WHEEL” on page 4-7.
2. Check:
• Brake disc
Damage/galling  Replace.
3. Measure:
• Brake disc thickness
Measure the brake disc thickness at a few
different locations.
Out of specification  Replace.
Refer to “CHECKING THE FRONT BRAKE
DISC” on page 4-15.
4. Measure:
• Brake disc deflection
Out of specification  Correct the brake disc
deflection or replace the brake disc.5. Adjust:
• Brake disc deflection
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the brake disc.
b. Turn the mounted position of the brake disc
by one bolt hole.
c. Install the brake disc.
TIP
Tighten the brake disc bolts in stages and in a
crisscross pattern.
d. Measure the brake disc deflection.
e. If out of specification, repeat the adjustment
steps until the brake disc deflection is within
specification.
f. If the brake disc deflection cannot be
brought within specification, replace the
brake disc.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
6. Install:
• Rear wheel
Refer to “REAR WHEEL” on page 4-7. Brake disc thickness limit
3.5 mm (0.14 in)
Brake disc deflection limit
0.15 mm (0.0059 in)
Brake disc bolt
14 Nm (1.4 m·kgf, 10 ft·lbf)
LOCTITE®
T R..

REAR BRAKE
4-26
EAS1SM1151REMOVING THE REAR BRAKE CALIPER
TIP
Before disassembling the brake caliper, drain
the brake fluid from the entire brake system.
1. Remove:
• Union bolt
• Copper washers
• Brake hose
TIP
Put the end of the brake hose into a container
and pump out the brake fluid.
EAS1SM1152DISASSEMBLING THE REAR BRAKE CALI-
PER
1. Remove:
• Brake caliper piston “1”
• Brake caliper piston dust seal “2”
• Brake caliper piston seal “3”
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Blow compressed air into the brake hose
joint opening to force out the piston from the
brake caliper.
EWA13550
WARNING
• Cover the brake caliper piston with a cloth.
Be careful not to get injured when the pis-
ton is expelled from the brake caliper.
• Do not use a screwdriver etc. for removing
the brake caliper piston.
b. Remove the brake caliper piston dust seal
and the brake caliper piston seal.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS1SM1153CHECKING THE REAR BRAKE CALIPER
1. Check:
• Brake caliper piston “1”
Rust/scratches/wear  Replace the brake
caliper piston.
• Brake caliper cylinder “2”
Scratches/wear  Replace the brake cali-
per assembly.
• Brake caliper body “3”
Cracks/damage  Replace the brake cali-
per assembly.
• Brake fluid delivery passages
(brake caliper body)
Obstruction  Blow out with compressed
air.
EWA13610
WARNING
When the brake caliper is disassembled, re-
place the brake caliper piston seal and the
brake caliper piston dust seal with new
ones.
2. Check:
• Brake caliper bracket
Crack/damage  Replace.
EAS1SM1154ASSEMBLING THE REAR BRAKE CALIPEREWA13620
WARNING
• Before installation, clean and lubricate the
internal parts. Use new brake fluid for
cleaning and lubricating.
• Never use solvents on internal brake com-
ponents as they will cause the piston seals
to swell and distort.
• When the brake caliper is disassembled,
replace the brake caliper piston seal and
the brake caliper piston dust seal with new
ones.
2
3
1
Recommended brake fluid
DOT 4
1 2
3

REAR BRAKE
4-27
EAS1SM1155INSTALLING THE BRAKE CALIPER PISTON
1. Clean:
• Brake caliper
• Brake caliper piston seal
• Brake caliper piston dust seal
• Brake caliper piston
Use brake fluid for cleaning.
2. Install:
• Brake caliper piston seals “1”
• Brake caliper piston dust seal “2”
EWA33DD033
WARNING
Always use new brake caliper piston seal
and brake caliper piston dust seal.
TIP
• Apply the brake fluid on the brake caliper pis-
ton seal.
• Apply the silicone grease on the brake caliper
piston dust seal.
• Fit the brake caliper piston seals and brake
caliper piston dust seals onto the slot on
brake caliper correctly.
3. Install:
• Brake caliper piston “1”
TIP
Apply the brake fluid on the piston wall.
ECA33DD047
NOTICE
• Install the piston with its side “a” facing
the brake caliper.
• Never force to insert.
EAS1SM1156INSTALLING THE REAR BRAKE CALIPER
1. Install:
• Rear brake caliper
• Rear brake caliper bracket
2. Install:
• Rear wheel
Refer to “REAR WHEEL” on page 4-7.
• Copper washers
• Brake hose
• Union bolt
EWA13530
WARNING
Proper brake hose routing is essential to in-
sure safe vehicle operation. Refer to “CA-
BLE ROUTING DIAGRAM” on page 2-31.
ECA14170
NOTICE
Make sure that a bend in its pipe portion “a”
is directed as shown and the brake hose
touches the projection “b” on the brake cal-
iper.
3. Install:
• Brake pad springs
• Brake pads
• Brake pad pin
• Brake pad pin plug
Refer to “CHECKING THE REAR BRAKE
PADS” on page 3-25.
4. Pour brake fluid to the brake fluid reservoir
up to the specified level.
New
New
2
1
1
a1
Brake hose union bolt
30 Nm (3.0 m·kgf, 22 ft·lbf)
Brake pad pin
17 Nm (1.7 m·kgf, 12 ft·lbf)
Brake pad pin plug
2.5 Nm (0.25 m·kgf, 1.8 ft·lbf)
Recommended brake fluid
DOT 4
New
T R..
b
b
a
T R..

REAR BRAKE
4-28
EWA13090
WARNING
• Use only the designated brake fluid. Other
brake fluids may cause the rubber seals to
deteriorate, causing leakage and poor
brake performance.
• Refill with the same type of brake fluid that
is already in the system. Mixing brake flu-
ids may result in a harmful chemical reac-
tion, leading to poor brake performance.
• When pouring the brake fluid, be careful
that water does not enter the reservoir.
Water will significantly lower the boiling
point of the brake fluid and could cause
vapor lock.
ECA13540
NOTICE
Brake fluid may damage painted surfaces
and plastic parts. Therefore, always clean
up any spilt brake fluid immediately.
5. Bleed:
• Brake system
Refer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-21.
6. Check:
• Brake fluid level
The minimum level mark “a” or below 
Add.
Refer to “CHECKING THE BRAKE FLUID
LEVEL” on page 3-26.
7. Check:
• Brake pedal operation
A softy or spongy feeling  Bleed the brake
system.
Refer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-21.
EAS1SM1157
REMOVING THE REAR BRAKE MASTER
CYLINDER
TIP
Before removing the rear brake master cylin-
der, drain the brake fluid from the entire brake
system.
1. Remove:
• Union bolt
• Copper washers
• Brake hose
TIP
To drain any remaining brake fluid, place a con-
tainer under the master cylinder and the end of
the brake hose.
EAS1SM1158CHECKING THE REAR BRAKE MASTER
CYLINDER
1. Check:
• Brake master cylinder “1”
Damage/scratches/wear  Replace.
• Brake fluid delivery passages “2”
(brake master cylinder body)
Obstruction  Blow out with compressed
air.
2. Check:
• Brake master cylinder kit
Damage/wear  Replace.
3. Check:
• Master cylinder reservoir cap
Crack/damage  Replace.
• Brake master cylinder reservoir diaphragm
holder
• Brake master cylinder reservoir diaphragm
Crack/damage  Replace.
4. Check:
• Brake hoses
Cracks/damage/wear  Replace.
EAS1SM1159
a
1
2